/*
 * Copyright 1999-2017 Alibaba Group Holding Ltd.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package studio.raptor.sqlparser.util;

/**
 * format validation This class encodes/decodes hexadecimal data
 *
 * @version $Id: HexBin.java,v 1.4 2007/07/19 04:38:32 ofung Exp $
 */
public final class HexBin {

  static private final int BASE_LENGTH = 128;
  static private final int LOOKUP_LENGTH = 16;
  static final private byte[] HEX_NUMBER_TABLE = new byte[BASE_LENGTH];
  static final private char[] UPPER_CHARS = new char[LOOKUP_LENGTH];
  static final private char[] LOWER_CHARS = new char[LOOKUP_LENGTH];

  static {
    for (int i = 0; i < BASE_LENGTH; i++) {
      HEX_NUMBER_TABLE[i] = -1;
    }
    for (int i = '9'; i >= '0'; i--) {
      HEX_NUMBER_TABLE[i] = (byte) (i - '0');
    }
    for (int i = 'F'; i >= 'A'; i--) {
      HEX_NUMBER_TABLE[i] = (byte) (i - 'A' + 10);
    }
    for (int i = 'f'; i >= 'a'; i--) {
      HEX_NUMBER_TABLE[i] = (byte) (i - 'a' + 10);
    }

    for (int i = 0; i < 10; i++) {
      UPPER_CHARS[i] = (char) ('0' + i);
      LOWER_CHARS[i] = (char) ('0' + i);
    }
    for (int i = 10; i <= 15; i++) {
      UPPER_CHARS[i] = (char) ('A' + i - 10);
      LOWER_CHARS[i] = (char) ('a' + i - 10);
    }
  }

  public static String encode(byte[] bytes) {
    return encode(bytes, true);
  }

  public static String encode(byte[] bytes, boolean upperCase) {
    if (bytes == null) {
      return null;
    }

    final char[] chars = upperCase ? UPPER_CHARS : LOWER_CHARS;

    char[] hex = new char[bytes.length * 2];
    for (int i = 0; i < bytes.length; i++) {
      int b = bytes[i] & 0xFF;
      hex[i * 2] = chars[b >> 4];
      hex[i * 2 + 1] = chars[b & 0xf];
    }
    return new String(hex);
  }

  /**
   * Decode hex string to a byte array
   *
   * @param encoded encoded string
   * @return return array of byte to encode
   */
  static public byte[] decode(String encoded) {
    if (encoded == null) {
      return null;
    }

    int lengthData = encoded.length();
    if (lengthData % 2 != 0) {
      return null;
    }

    char[] binaryData = encoded.toCharArray();
    int lengthDecode = lengthData / 2;
    byte[] decodedData = new byte[lengthDecode];
    byte temp1, temp2;
    char tempChar;
    for (int i = 0; i < lengthDecode; i++) {
      tempChar = binaryData[i * 2];
      temp1 = (tempChar < BASE_LENGTH) ? HEX_NUMBER_TABLE[tempChar] : -1;
      if (temp1 == -1) {
        return null;
      }
      tempChar = binaryData[i * 2 + 1];
      temp2 = (tempChar < BASE_LENGTH) ? HEX_NUMBER_TABLE[tempChar] : -1;
      if (temp2 == -1) {
        return null;
      }
      decodedData[i] = (byte) ((temp1 << 4) | temp2);
    }
    return decodedData;
  }
}
